There are many different configurations of hybrid and/or all electric vehicles. Some embodiments of hybrid vehicles provide drive torque to the wheels of both a front axle and the wheels of a rear axle. Accordingly, the wheels of the front axle are provided with drive torque to propel the vehicle, as well as the wheels of the rear axle being provided with drive torque to propel the vehicle. The wheels of the front axle and the wheels of the rear axle may be provided with their respective drive torque by one or more power sources, which may include but are not limited to an internal combustion engine and/or an electric motor. For example, a front axle may be powered by an electric device, and the rear axle may be powered by an internal combustion engine. Alternatively, all the wheels of the front axle, and all the wheels of the rear axle may each be powered by independent electric devices.
The front axle and the rear axle may be either coupled, or de-coupled. If the front axle and the rear axle are coupled, then the first axle and the second axle are mechanically linked together, and are capable of directly transferring torque therebetween. If the front axle and the rear axle are de-coupled, then the front axle and the rear axle are not mechanically linked together, may be considered separated mechanical systems, and are not capable of directly transferring torque therebetween.
Hybrid vehicles may convert kinetic energy from the rotating wheels into some other form of energy. For example, hybrid vehicles using an electric device to provide a propulsive force to an axle typically include an energy storage device, e.g., a battery or other similar device. The energy storage device must be charged, referred to herein as regeneration. Regeneration of the energy storage device may be accomplished in several different ways. For example, the energy storage device may be regenerated through a regenerative braking process, in which energy used to decelerate the vehicle is converted into electrical energy that is stored in the energy storage device. The regenerative braking process may be implemented at one or both of the front axle and/or the rear axle. Alternatively, the electric device (or a second electric device) may be operated as a generator to charge the energy storage device. The control strategy used to control the internal combustion engine and/or the electric device determines how the energy storage device is regenerated for specific, different vehicle dynamic operating conditions, such as forward acceleration or deceleration, lateral acceleration, engine torque, etc. Alternatively, the kinetic energy from the wheels may be converted into a form of energy other than electrical energy. For example, the energy storage device may include a weighted flywheel, in which case the kinetic energy from the wheels is transferred to kinetic energy of the flywheel.